The present invention relates to a sealing tool and a process for sealing a package trough with a covering film.
Packages, particularly packages for foods, are becoming increasingly important today in the preservation of foods. For packaging, the foods are placed in a so-called package trough and the package trough is then closed in a gas-tight manner with a covering film by sealing the covering film onto the edge of the package trough.
Usually, the package troughs are semi-continuously sealed with a covering film in so-called sealing stations. To this end, the package trough filled with the packaged good and the covering film are initially fed into the sealing station. As soon as the package trough is situated in the sealing station, a first bottom sealing tool is raised vertically from below and pressed against a second, heated top sealing tool, which is located above the covering film. As a result of the pressure and temperature applied, the covering film and the edge of the package trough, which are situated between the sealing tools, are sealed. In order to obtain gas-tight seal seam, it is important that the seal seam have a certain width and that the seal seam be essentially situated in the middle of the edge of the package trough. After sealing, the first sealing tool is lowered back beneath the freshly sealed package trough, and the sealed package trough is fed on to the cutting station.
Although this type of a sealing station has been in use for many years, it nevertheless displays a number of disadvantages. For instance, package troughs having an undercut cannot be sealed with such a sealing tool, because the first sealing tool collides with the undercut during lifting and lowering and thereby destroys it. However, even with packages that do not have an undercut, problems repeatedly occur during the sealing of heavily loaded package troughs, because these package troughs sag. Because of this sagging, the package troughs tilt and the first sealing tool on its ascent collides with the corners and thereby destroys or deforms them.